“Water blooms” (algas in water body) have become a global environmental issue, and cause great harm to the utilization of water resources, for example, drop of dissolved oxygen in water, and threat of algal toxins released by algas to biological lives or the like, wherein microcystis aeruginosa is the major species of “water blooms”, which is dominant in quantity and outbreak frequencies. How to control the microcystis aeruginosa becomes a difficult problem for more and more scientists and researchers to solve Lake Eutrophication.
There are many methods for removing algas at present, wherein mechanical alga removal can quickly and effectively remove the algas and algal tufa in the water in a short term, but consume a lot of human and material resources; and chemical alga removal can also kill the algas quickly, but the secondary pollution caused by the dead algas as well as the biological concentration and biological magnification of chemicals cause larger negative influences to the entire ecological system. In recent years, non-traditional biomanipulation technology has been widely applied in Lake Eutrophication treatment. For example, Chinese patent (No. 200710071818.2) discloses an inventive patent titled as bighead carp, grass carp, cladophora and daphnia hyaline multi-biology cooperated algae control method. The method according to the disclosure includes the following steps of: putting bighead and grass carp in an eutrophication water body, the putting proportion of the bighead and the grass carp is 3:1˜4:1; placing floating cages in the eutrophication water body, with cladophora adhered on the cages; and putting daphnia hyalina in the cages. According to the disclosure, the bighead and the grass carp eat the algas in the eutrophication water body in a filtering manner, and the cladophora removes the nutrients in the water body; therefore, the objects of controlling the contents of algas in the raw water, reducing the trophic level of the raw water, and facilitating conventional treatment of tap water are achieved. For another example, Chinese patent (No. 200910197309.3) discloses a control method for alga control method for freshwater environment based on cultivation of barracudas and mullets, which introduces one of estuarine and oceanographic fishes like barracudas and mullets which can be only propagated in seawater with respect to the problem that the algas in the eutrophication water body and freshwater body cannot be stably and thoroughly controlled, and brings nitrogen and phosphorus nutrients in the water and humic substances in bottom materials out of the water body through harvesting the hydrobiontes propagated via cultivating. Chinese patent (No. 200710151009.2) discloses a technical method for silver carp and hyriopsis cumingii combined algae-controlling, which removes the nutritive salt in a water body like nitrogen, phosphorus or the like through the cooperative effects of chub and hyriopsis cumingii for controlling algas.
The above non-traditional biomanipulation technology can remove cyanophytes, but cannot control the cyanophytes in each water zone. Moreover, excrements of these fishes still contain some undigested cyanophytes which will grow again in case of being sedimentated into the bottom layer of the water body; therefore, the removal effect thereof is not ideal. Although biological alga removal can be derived in the art, the core problem above is that these methods cannot achieve long term ecological balance, while this is just the difficult aspect to control for biological alga removal because the most difficult point to artificially establish and control an ecological environment is whether the algas can be removed for a long term rather than whether the algas can be removed. An optional scheme is to control the cyanophytes within a reasonable range, prompting the put organisms and cyanophytes to form a complete ecological chain, which is the key of the technology. Moreover, the control systems for different organisms are different as well, and seldom reports can be found in the existing literatures, which leads to fewer actual engineering application examples to control the microcystis aeruginosa by using organisms.